+Bjorn On Mon, Oct 10, 2016 at 8:33 AM, Rob Herring <[email protected]> wrote: > On Mon, Oct 10, 2016 at 8:17 AM, Laszlo Ersek <[email protected]> wrote: >> Hi, >> >> Greg asked me to stick to email with this bug report, so I'm reposting >> the original kernel bugzilla report to personal addresses, and lkml. >> >> Thanks, >> Laszlo >> >> https://bugzilla.kernel.org/show_bug.cgi?id=177021 >> >> Bug ID: 177021 >> Summary: [driver core] CONFIG_DEBUG_TEST_DRIVER_REMOVE causes >> unremovable drivers to bind devices twice >> Product: Drivers >> Version: 2.5 >> Kernel Version: v4.8-2283-ga3443cd (4.9.0-0.rc0.git2.1.fc26.aarch64) >> Hardware: All >> OS: Linux >> Tree: Mainline >> Status: NEW >> Severity: normal >> Priority: P1 >> Component: Other >> Assignee: [email protected] >> Reporter: [email protected] >> CC: [email protected], [email protected] >> Regression: No >> >> CONFIG_DEBUG_TEST_DRIVER_REMOVE was added in the following commit: >> >>> commit bea5b158ff0da9c7246ff391f754f5f38e34577a >>> Author: Rob Herring <[email protected]> >>> Date: Thu Aug 11 10:20:58 2016 -0500 >>> >>> driver core: add test of driver remove calls during probe > > [...] > >> This is almost a regression because the kernel crashes with valid >> drivers. It is not an error for a driver to not provide a remove() >> callback, so in this instance CONFIG_DEBUG_TEST_DRIVER_REMOVE does not >> expose a driver bug, it breaks with a valid driver. Not a regression for >> the upstream kernel after all, because the Kconfig documentation >> suggests N as default. >> >> Proposed solution: if none of the remove() methods exist, or the >> remove() method that exists fails, then don't release any resources, and >> don't re-probe the device. > > I was thinking no remove method meant the driver didn't need to do any > explicit clean-up as all resources used devres, but I guess that's not > going to cover things like subsystem de-registration. I'll prepare a > fix.
Looking at this some more, I think this should just be keyed off of suppress_bind_attr. If userspace provides bind/unbind for a driver, then remove and re-probe should work even if the driver doesn't have a remove function. Either the generic PCI host needs to set suppress_bind_attr like many of the ARM-based PCI host drivers already do or the remove path should be fixed to support this. Getting PCI hosts to be hot plug-able is a goal (or maybe supported now?). Rob
